We, or at least I, can have no conception of human life and human thought in a hundred years or fifty years. Perhaps my greatest wisdom is the knowledge that I do not know. The sad ones are those who waste their energy in trying to hold it back, for they can only feel bitterness in loss and no joy in gain.

John Steinbeck (1902-1968) American writer

Travels With Charley: In Search of America, Part 2 (1962)